The WHERE CURRENT OF clause is used in some UPDATE and DELETE statements.
The WHERE CURRENT OF clause in an UPDATE or DELETE statement states that the most recent row fetched from the table should be updated or deleted. We must declare the cursor with the FOR UPDATE clause to use this feature.
Inside a cursor loop, WHERE CURRENT OF allows the current row to be directly updated.
When the session opens a cursor with the FOR UPDATE clause, all rows in the return set will hold row-level exclusive locks. Other sessions can only query the rows, but they cannot update, delete, or select with FOR UPDATE.
Oracle provides the FOR UPDATE clause in SQL syntax to allow the developer to lock a set of Oracle rows for the duration of a transaction.
WHERE [CURRENT OF cursor_name | search_condition]
CREATE OR REPLACE function findCourse ( name_in IN VARCHAR2 ) RETURN NUMBER IS cnumber NUMBER; CURSOR c1 IS SELECT course_number FROM courses_tbl WHERE course_name = name_in FOR UPDATE of instructor; BEGIN OPEN c1; FETCH c1 INTO cnumber; IF c1%NOFOUND THEN cnumber := 9999; ELSE UPDATE courses_tbl SET instructor = 'SMITH' WHERE CURRENT OF c1; COMMIT; END IF; CLOSE c1; RETURN cnumber; END;
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